1. Field of the Invention
The present invention relates to an electric motor, and in particular to an improvement of structure for connecting electric cables with internal cables of the electric motor.
2. Description of Related Art
As well known in the art, electric cables such as power cables are connected to terminals of internal cables of an electric motor for supplying electricity to the motor and other purposes. In approaching and connecting the electric cables to the terminals of the internal cables, a high degree of freedom in selecting a direction of the approach and connection of the electric cables has been required by factors such as a design of the motor, a direction of installation of the motor and a relative position of the motor with respect to a plug socket.
The electric cables for power supply are difficult to be handled in a wiring work since they are generally thick and hard. Further, there is not a sufficient space for the wiring work in a machine into which the electric motor is already assembled. Thus, it is desirable to have a high degree of freedom in selecting a direction of the approach and connection of the electric cables to the electric motor in order to facilitate the wiring work.
It is also necessary to avoid exposure of connecting portions of the electric cables and the internal cables to exterior of the electric motor for securing a human safety, preventing a short circuit by contamination of the connecting portions, and preventing an external force on the connecting portion. Thus, a terminal case surrounding the connecting portion and having a through hole for introducing the electric cables has been adopted, or a through hole is formed on a body of the electric motor for introducing the electric cables.
In order to obtain high degree of freedom of direction of the approach and connection of the electric cables, there are proposals of (1) forming through holes for introducing the electric cables at different positions in a terminal case, (2) preparing a plurality of types of electric motors having a terminal case with a through hole at a different position to be selected in accordance with request of an user, (3) providing structure for easily forming a through hole, such as perforation, at one of different positions so that a through hole is formed at a desired position in connecting the electric cables to the electric motor, (4) providing a plurality of through holes at different positions on a body of an electric motor.
The above proposals have respective problems as flows; In the case of proposals (1) and (4), it is necessary to provide plugs for closing the holes which are not used for introducing the electric cables so as to prevent invading of liquid and dust from the open holes. There also arises a problem that shape of the terminal case or the body has to be complicated to raise manufacturing cost. In the case of proposal (2), it is cumbersome and uneconomical to prepare a plurality of types of electric motors and select one type of the electric motor for a manufacturer and also a user. In the case of proposal of (3), the through hole once formed remains open and it is costly to provide structure such as perforation for easily forming a through hole at different position.
An object of the present invention is to provide an electric motor having a sufficient degree of freedom in selecting a direction of approaching and connecting the electric cables to the internal cables without the above problems in the prior art.
An electric motor of the present invention comprises: a body containing internal cables; and a cable introducing member having a through hole for introducing the electric cables for connection with the internal cables. The cable introducing member is detachably mounted on the body to have one of a plurality of different orientations such that a position of the through hole relative to the body is selectable from a plurality of different positions.
With the above arrangement, a high degree of freedom is secured in selecting a direction of the approach and connection of the electric cables to the electric motor of the same kind using the same cable introducing member, without forming redundant through holes for obtaining the high degree of freedom. Thus, invading of water and dust into the motor from the unused through holes is prevented and it is not necessary to close the unused through holes. Further, the position of the through hole relative to the body of the electric motor can be changed by detaching the cable introducing member from the body and mounting the cable introducing member again on the body to have a different orientation.
The plurality of orientations of the cable introducing member may be angularly displaced by a predetermined angle.
The cable introducing member may have a cross section of a regular polygon, or an annular cross section.
The electric motor may further comprise a terminal rest fixed to the body for allowing connection of the electric cables with the internal cables in at least two different directions. The terminal rest may have a plurality of terminals including an upper terminal and a lower terminal positioned at different heights.